Real Dictionary

doormat
countable noun: A doormat is a mat by a door which people can wipe their shoes on when they enter a house or building.
countable noun: If you say that someone is a doormat, you are criticizing them because they let other people treat them badly, and do not complain or defend themselves when they are being treated unfairly.

doormat in American English
a mat for people to wipe their shoes on before entering a house, room, etc.
noun: a mat, usually placed before a door or other entrance, for people arriving to wipe their shoes on before entering

doormat in British English
noun: a mat, placed at the entrance to a building, for wiping dirt from shoes